1. Field of the Invention
The present invention relates to a liquid crystal display element and a liquid crystal display device employing the same, e.g., a liquid crystal projector.
2. Description of the Related Art
The liquid crystal display modes for the reflection type liquid crystal light valve employing a nematic liquid crystal are roughly classified into the three kinds of systems. That is, there are a tilted homeotropic ECB (Electrically Controlled Birefringence) mode, a homogenious ECB mode and a reflection type twisted nematic mode.
By the tilted homeotropic ECB mode is meant the alignment system in which the liquid crystal molecules are arranged in such a way as to be slightly inclined with respect to the perpendicular direction of each of a pair of substrates by utilizing the oblique evaporation method or the like, and this mode is described in an article of Applied Physics Letters 20, 199 (1972) for example.
By the homogenious ECB mode is meant the alignment system in which the liquid crystal molecules are arranged in such a way as to be roughly parallel to each of a pair of substrates, and this mode is described in JP-A-1-7021.
Also, by the reflection type twisted nematic mode is meant the system in which the liquid crystal molecules are arranged in such a way as to be roughly parallel to each of a pair of substrates and also the alignment directions in the vicinity of the pair of substrates holding therebetween the liquid crystal molecules shows the twisted positional relationship. By the way, for the twisted nematic mode, the several systems have been further proposed. As an example, there are an HFE (Hybrid Field Effect) mode, a TN-ECB (Twisted Nematic-Electrically Controlled Birefringence) mode, an SCTN (Self-Compensated Twisted Nematic) mode, an MTN (Mixed mode Twisted Nematic) mode, and the like.
The TN-ECB mode is described in an article of Japan Display '89, p. 192 (1989), the SCTN mode is described in JP-A-10-090731, and the MTN mode is described in an article of Applied Physics Letters 68, p. 1455 (1996). In addition, the inclusive analysis of the overall reflection type twisted nematic mode is described in an article of Proceedings of SPIE 3635, p. 87 (1999) and an article of Proceedings of IDW '99, p. 985 (1999).
By the way, of these modes, the HFE mode is the so-called normally black type display mode which becomes the black (dark) display when the voltage applied thereto is 0 Vrms, while becomes the white (light) display when a suitable voltage is applied thereto. Each of other three modes is the so-called normally white display mode which becomes the white (light) display when the applied voltage is 0 Vrms, while becomes the black (dark) display when a suitable voltage is applied thereto.
The typical system as the optical system employing these reflection type liquid crystal light valves is the optical system employing the polarizing beam splitter and it is described in JP-A-61-13885. In addition, as for other example, the optical system in which the main optical axis is made oblique with respect to the vertical direction of the liquid crystal light valve is described in JP-A-4-319910.
By the way, as for the technique in which the reflection type liquid crystal light valve and the retardation plate are combined with each other, the technique in which the polarizing beam splitter, the ¼ wave plate and the reflection type liquid crystal light valve are combined with one another and these elements are arranged in such a way that the fast axis or the slow axis of the ¼ wave plate intersects perpendicularly the flat surface containing the incident light axis and the reflected light axis of the polarizing beam splitter is disclosed in JP-A-2-250026 and U.S. Pat. No. 5,327,270. In addition, the technique in which the retardation of the retardation plate combined with the polarizing beam splitter is made equal to or larger than 0.25 (i.e., ¼ wavelength) is disclosed in U.S. Pat. No. 5,576,854. Also, the description of the polarizing controller including the double refraction material layer is made in JP-A-1-7021.